Like the circuit of the invention, the conventional automatic shut-off and transient holding type charging circuit uses a voltage or current detector device constituted by electronic components to charge a chargeable battery. The circuit includes a temperature switch which senses the temperature of the chargeable battery so that when the battery is saturated and the temperature is raised, the charger is switched to provide a smaller current input to the battery.
However, the conventional automatic shut-off and transient state holding type charge circuit is comprised of numerous components, and has a complicated structure with high cost and low reliability.
The circuit of the invention uses a temperature switch to control automatic shut-off, but with a less complicated and lower cost structure for applications involving a wider voltage range than the conventional circuit.
According to the invention, when the battery is charge to saturation, and when the battery temperature is raged to a preset value, the temperature control switch is actuated, which causes the circuit to automatically switch to a small current. The small current maintains the charging status before the temperature switch is automatically reset, so that it is within the predetermined power source voltage variation range. Reset occurs when the battery is removed or the power source is cut off, and to include return current diode for providing an automatic emergency power supply function.